Major efforts are currently being expended to clean up contaminated soils throughout the United States and the world. Such contaminated soils typically arise as industrial products or by-products which are spilled either inadvertently or purposely into the environment. Commonly found contaminants are herbicides. pesticides, petroleum products and other hazardous industrial by-products. The time and expense involved in removing these contaminants from soil is frequently immense. Further, some soil types can exacerbate the problem by tightly binding with contaminants. Soils with a heavy clay content are frequently exceedingly difficult to decontaminate because of such binding actions.
Interestingly, in many contamination sites there will exist naturally-occurring microorganisms which have a capacity to aid in removal of the contaminant from the environment. Methods by which such micro-organisms can aid in removal of contaminants vary. Sometimes the contaminants are actually degraded, either partially or totally, by the microorganisms. Othertimes, the microorganisms can convert a contaminant to a substance which binds less tightly to the soil and is therefore easier to remove from the soil. In addition to the naturally-occurring microorganisms which may aid in removal of contaminants, non-naturally-occurring microorganisms may also be utilized. Such non-naturally-occurring microorganisms may sometimes be created by skilled scientists for the purpose of removing a contaminant from the environment. Example microorganisms which may be useful in remediating contaminated soils are described in U.S. Pat. No. 5,387,271, to Crawford et. at., entitled "Biological System For Degrading Nitroaromatics In Water And Soils," which is incorporated herein by reference.
In spite of the knowledge that naturally occurring and non-naturally-occurring microorganisms can aid in removal of contaminants from soils, and, in spite of frequent speculation that such microorganisms may be useful in remediating contaminated soil sites, it has been a considerable challenge to develop devices and procedures which can efficiently tap the utilities of such microorganisms. Among the problems faced are: 1) the microorganisms are frequently anaerobic so that oxygen must be substantially excluded from the environment of the microorganisms if they are to function efficiently; 2) the microorganisms, or some substance formed by the microorganisms, must generally contact a contaminant before the microorganisms can efficiently aid in removing the contaminant, so there must be efficient mixing of the microorganisms with a contaminated soil; and 3) the contaminated sites are generally enormous, possibly several square miles or larger in size. It is desirable therefore to develop methods and apparatuses which can be used in conjunction with microbiological activity to clean up contaminated soil sites.
Another set of problems facing those who would remediate contaminated soil sites concern the difficulties in preventing spillage of contaminated soil during the remediation process. Spilled contaminated soil may contaminate areas that were previously clean. Such spillage is particularly likely to occur during transport of the contaminated soil, as the soil may become a dust which is wind-blown to clean areas, or may be dribbled from open containers, or trucks, passing over the clean areas. Accordingly, it would be desirable to develop methods and apparatuses which minimize spread of contaminated soil from a remediation site during a remediation process.
Yet another set of problems facing those who would remediate contaminated soil sites arises from the remote locations of the sites. Frequently, such sites lack access to electrical power and lack nearby facilities for repair of broken equipment. Accordingly, it would be desirable to minimize the power requirements of decontamination apparatuses utilized at the sites, and to provide relatively durable decontamination apparatuses.